Narrative:

We were descending into clt with a clearance of 9000 ft. The first officer made his callout of 10000 ft for 9000 ft, which I acknowledged and I called 'out of 10000 ft, light on, approach checklist.' he accomplished the checklist and the next thing I remember was the altitude alerter going off. I checked my altitude at 8700 ft, checked the alerter set at 9000 ft and climbed immediately to 9000 ft. The controller asked what our altitude was as we arrived back at 9000 ft. A short while later he pointed out converging traffic at 8000 ft and 3 mi. At the time of the excursion, I don't think we had a traffic conflict. I think fatigue was a factor in this event. Due to labor problems at our airline, this was my 13TH consecutive day of work and the 9TH back side of the clock operation. (Twice during this period I had approximately a 60 hour break without duty.) additionally, I had worked 21 of the last 23 days. I remember the alerter as total shock, like an alarm waking me up. I'm sure I wasn't asleep, but I think my 'lights were on, and nobody was home.' sometimes the XA00-XC00 time period is a bad time for me and I think too much work has aggravated it. I'll just have to be more careful to prevent a recurrence. My vacation is close, and I'll be taking care of any sleep deficit.

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Original NASA ASRS Text

Title: AN ACR DC9 FLC DSNDED THROUGH THEIR ASSIGNED ALT. THE CAPT FEELS THAT FATIGUE PLAYED A PART AND THE FO WAS DISTR BY ANOTHER DUTY AT THE TIME.

Narrative: WE WERE DSNDING INTO CLT WITH A CLRNC OF 9000 FT. THE FO MADE HIS CALLOUT OF 10000 FT FOR 9000 FT, WHICH I ACKNOWLEDGED AND I CALLED 'OUT OF 10000 FT, LIGHT ON, APCH CHKLIST.' HE ACCOMPLISHED THE CHKLIST AND THE NEXT THING I REMEMBER WAS THE ALT ALERTER GOING OFF. I CHKED MY ALT AT 8700 FT, CHKED THE ALERTER SET AT 9000 FT AND CLBED IMMEDIATELY TO 9000 FT. THE CTLR ASKED WHAT OUR ALT WAS AS WE ARRIVED BACK AT 9000 FT. A SHORT WHILE LATER HE POINTED OUT CONVERGING TFC AT 8000 FT AND 3 MI. AT THE TIME OF THE EXCURSION, I DON'T THINK WE HAD A TFC CONFLICT. I THINK FATIGUE WAS A FACTOR IN THIS EVENT. DUE TO LABOR PROBS AT OUR AIRLINE, THIS WAS MY 13TH CONSECUTIVE DAY OF WORK AND THE 9TH BACK SIDE OF THE CLOCK OP. (TWICE DURING THIS PERIOD I HAD APPROX A 60 HR BREAK WITHOUT DUTY.) ADDITIONALLY, I HAD WORKED 21 OF THE LAST 23 DAYS. I REMEMBER THE ALERTER AS TOTAL SHOCK, LIKE AN ALARM WAKING ME UP. I'M SURE I WASN'T ASLEEP, BUT I THINK MY 'LIGHTS WERE ON, AND NOBODY WAS HOME.' SOMETIMES THE XA00-XC00 TIME PERIOD IS A BAD TIME FOR ME AND I THINK TOO MUCH WORK HAS AGGRAVATED IT. I'LL JUST HAVE TO BE MORE CAREFUL TO PREVENT A RECURRENCE. MY VACATION IS CLOSE, AND I'LL BE TAKING CARE OF ANY SLEEP DEFICIT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.